#WSO2 #Ballerina #Microservices #Integration #API
Every developer has a list of small "helper" services they plan to build but never get around to. For my Ebook Reader application, one of those was a service to find a book's ISBN. The data was scattered — some in my database, some on public APIs. I needed a single, fast way to get it.
I’d been hearing a lot about WSO2 Ballerina and how it’s designed specifically for integration. I decided it was time to finally learn it, and this ISBN helper service felt like the perfect first project to tackle.
🔧 Why Ballerina for a First Project?
When learning a new language, I find it's best to build something real. The problem of fetching and caching data from multiple sources is a common one, and Ballerina's features seemed to address it directly.
Instead of just learning syntax, I wanted to see how a language performs on a real integration task. Ballerina’s focus on network services, APIs, and JSON handling made it a practical choice, not just an academic exercise.
📖 Introducing: Title2ISBN Service
A Ballerina-based microservice that acts as a smart caching layer. When my Ebook Reader app needs an ISBN for a book title, it asks this service. The service checks its own cache (an Appwrite database) and only calls the external Open Library API if it's a new book.
Core Features
- ⚡️ Caching logic to reduce latency
- 📞 Fetches data from external REST APIs
- 💾 Persists new data to an Appwrite DB
- 📦 Provides a single, clean REST endpoint
- 📊 Includes comprehensive logging
It’s a simple, focused microservice that solves one problem really well, and it was a great way to learn Ballerina.
🤖 How WSO2 Ballerina Helped
The real magic happened in the VS Code extension.
The Ballerina Visualizer was incredibly useful. It automatically generated a sequence diagram of my code as I was writing it. I didn't have to draw anything. As someone new to the language, I could literally see my logic:
- Request comes into the service.
- A branch appears:
if book in cache? - The "Yes" path goes straight to the final response.
- The "No" path shows the call to the Open Library API, then another call to the Appwrite API to save the result, and then the final response.
Seeing this visual flow confirmed my logic was sound and made debugging much easier. The language itself, with its record types for handling JSON and its straightforward http:Client, made the networking code feel clean and safe.
🏗️ Project Architecture
| Component | Purpose |
|---|---|
| REST API Layer | Exposes the /isbn endpoint to the main application. |
| Caching Logic | The core if/else block that decides to query the cache or fetch externally. |
| Appwrite Connector | The HTTP client code responsible for talking to the Appwrite database. |
| External API Connector | The HTTP client code for fetching data from the Open Library API. |
| Data Models | record types in Ballerina that define the shape of our data for type-safety. |
The service is designed to be a small, independent part of my larger Ebook Reader application ecosystem.
🚧 Known Issues
- Only queries one external data source (Open Library) for now
- Error handling is basic
- No price comparison or other metadata is fetched yet
- Needs proper deployment setup
But that's okay. The primary goal was to learn the language by building a working, efficient caching service.
📈 What’s Next?
Short-Term:
- Add Google Books as a fallback data source
- Refine error handling and response codes
Long-Term:
- Containerize the service with Docker
- Deploy to a cloud platform like WSO2 Choreo
- Build another Ballerina service for price comparison
🎁 Final Thoughts
Diving into a new language can be tough, but choosing a real-world problem made learning Ballerina much more effective. It wasn’t just about syntax; it was about seeing how the language’s features directly solve common integration headaches.
Ballerina didn't just help me write code; its tools helped me visualize and understand it.
Check out the repo: GitHub – Walapalam/title2isbn-service Fork it, watch it, or try running the build.
#WSO2 | #Ballerina | #Microservices | #Integration | #API